This invention relates to safety needles of the type used to puncture the skin of patients. More particularly, this invention relates to intravenous catheters that protect the needle both before use and upon withdrawal from a patient.
Safety needles and catheters are old in the art. For example, safety catheters are disclosed in: (1) U.S. Pat. No. 4,834,718 ("the '718 patent") issued on May 30, 1989, to Michael McDonald; and (2) U.S. Pat. No. 4,944,725 ("the '725 patent"), issued on Jul. 31, 1990, to Michael McDonald. Mr. McDonald is one of the inventors of the present invention in this application.
The catheter in the '718 patent was the first catheter to provide convenient, reliable, economical, and automatic sheathing of the needle upon withdrawal of the needle from the patient. The '725 patent discloses improvements to Mr. McDonald's first patented structure in the '718 patent. The applicants hereby incorporate by reference the complete disclosures of the '718 and '725 patents.
The structures shown in the '718 and '725 patents were significant advances in the art. They included "flash back" chambers to determine, by relatively small sliding movement of an outer housing away from the catheter, whether the vein had been punctured sufficiently so that blood would flow through the catheter and needle into the flash back chamber where the blood could be seen at the back of the housing.
These prior structures, however, were not as effective in drawing blood into the flash back chamber when used on trauma patients with very low blood pressure. For these types of patients, the blood pressure of the patient can be too low to force blood through the catheter and needle into the flash back chamber in the housing. These prior art devices did not provide any way to draw a substantial vacuum in the housing in order to draw blood from the trauma patient into the flash back chamber when the needle and associated catheter penetrate the vein of the patient.
Other safety needles in the art have employed plungers penetrating the back of the needle housing to draw a vacuum in the housing. None of these prior art structures, however, have provided such a vacuum plunger for the McDonald safety needles shown in the '718 and '725 patents.
Another problem with the prior art safety catheters and needles is the lack of capping structure for complete capping of the entire needle and catheter during assembly, shipping, and pre-use handling. Thus, the prior art catheters and needles such as shown in the '718 and '725 patents provided an exposed needle during needle assembly and shipping. The needles are also exposed when removed from their packaging and prior to actual alignment for injection into the patient. This brings about risk of inadvertent needle sticks to manufacturers and needle operators, and subsequent inappropriate use of the same needles on patients. Accidental needle sticks can have dire consequences and have long been recognized as a great problem in the industry and, indeed, in society in general.
Needles such those shown in the '718 patent and '725 patent do sheath the needle upon withdrawal from the patient. This provides the great advantage of automatic sheathing and protection against needle sticks upon withdrawal, but it leaves the operator without the comfort of having taken any action on his or her own to cover the needle. Existing paramedics, nurses, and doctors in the field are often accustomed to the prior art devices that do not automatically sheath the needle upon withdrawal from the patient. These types of operators are often most comfortable with capping of the needle whether it is necessary or not. The prior safety catheters of the '718 and '725 patents, and other safety catheters in the prior art, did not provide any such additional capping feature, probably because it appears to be unnecessary. It is often necessary, in fact, however, since such a cap can put certain types of operators at ease and reduce their reluctance to use a safety needle such as that shown in the '718 and '725 patents.
The prior McDonald safety catheters of the '718 and '725 patents incorporated needle hub design that had a reduced and thin neck (shown as number 36 in FIG. 1 of the '718 patent). This neck is easy for the operator to grasp and hold in place with one hand while simultaneously, with the other hand, pulling back on the outer housing and thus automatically sheathing the needle within the needle housing. The reduced diameter neck is relatively weak, however, and may be subject to breakage when in use out in the field.
Finally, the prior McDonald safety catheter employed a cylindrical outer housing with a smooth, transparent plastic surface. The operator grasps and pushes and pulls on the this smooth surface when using the device out in the field. Although this cylindrical transparent design is particularly effective and reliable for a number of reasons, the operator's fingers can slip on the smooth surface, particularly when wet, and risk puncturing the patient incorrectly or at least not as accurately as desired. An incorrectly positioned needle puncture, which misses the vein or goes through it, can be painful and cause bleeding.